Generally, the turning radius of the commercially available articulated bus is very large, and thus the articulated bus cannot be directly reversed. In the urban areas without exclusive bus lanes, the routing arrangement is difficult and has many restrictions. For increasing the operative and practical values of the articulated bus, it is necessary to develop an active steering system. Consequently, the articulated bus can provide better service in the areas with restricted road intersections or road curves.
Conventionally, an articulated joint provides a passive damping force to stabilize an articulated joint. For example, a mechanical damping means or a hydraulic damping means is usually used. The conventional articulated joint and the steering system and the vehicle control unit usually belong to different systems. For providing an active steering system, it is necessary to integrate the articulated joint into the vehicle control unit.
Industrially, an articulated trailer used to transport raw materials or goods has mechanical steering joints or hydraulic steering joints (or referred as tractor joints) for changing the travelling direction in response to the applied force. However, these tractor joints are directly controlled according to the position of the steering wheel. Moreover, the tractor trailers are unlike the articulated bus that uses a set of steering front wheels to change the advancing direction. In other words, the mechanical steering joint or the hydraulic steering joint is the only way for the tractor trailer to change the advancing direction. The present invention provides an articulated joint capable of actively assisting in the steering operation. By slowly applying a steering force and locking the joint at an optimal angle, the articulated joint can be controlled. That is, the articulated joint is not proportionally or directly linked to the position of the steering wheel.